The present invention relates to a brake hydraulic pressure control unit for a vehicle for controlling hydraulic pressures in the wheel cylinders mounted to the respective wheels of the vehicle based on commands from an electronic control unit.
Such brake hydraulic pressure control units, which are used in vehicle hydraulic brake systems having such functions as anti-lock brake control (ABS) and electronic stability control (ESC) functions, comprise a hydraulic block including a housing, and pumps and solenoid valves mounted to the housing, a motor for driving the pumps, and an electronic control unit including a motor driving circuit and solenoid valve control circuits. The solenoid valves include those for opening and closing brake fluid passages extending from the master cylinder to the wheel cylinders, and/or those for controlling hydraulic pressures in the respective wheel cylinders. A pressure sensor or sensors are optionally mounted in the hydraulic block.
Some of such brake hydraulic pressure control units have the motor mounted on one side of the hydraulic block and the electronic control unit mounted on the opposite side of the hydraulic block, as disclosed in JP patent publications 10-059152A and 10-278771A.
There is also known an arrangement in which the motor and the electronic control unit are provided on one side of the hydraulic block so as to be aligned in the axial direction of the motor. It may also be possible to provide the electronic control unit around the motor. But according to the type of vehicle, a brake hydraulic pressure control unit may be required in which the motor and the electronic control unit are mounted on one and the opposite sides of the hydraulic block, respectively, so as to face each other.
If such a brake hydraulic pressure control unit, which is mounted in the engine room of a vehicle, is too large in size (external dimensions), it may not be received in the installation space in the engine room according to the type of vehicle, and thus may not be mounted on the vehicle. It is therefore important that such control unit be as small in size as possible. But because in conventional arrangements of brake hydraulic pressure control units, their component parts forming the various circuits of the unit are typically arranged in the horizontal direction. This naturally results in increased lateral width (horizontal dimension) of the hydraulic block, thus making it more difficult to mount the control unit on a vehicle.
Many vehicles have their engine rooms designed such that vertically elongated brake hydraulic pressure control units can be more easily mounted therein than laterally elongated such units. But with brake hydraulic pressure control units in which the component parts forming the plurality of circuits thereof are arranged in the lateral direction, the lateral width of their hydraulic blocks is necessarily large. It is difficult to mount such control units in engine rooms designed such that vertically elongated units can be more easily mounted therein.
Ordinarily, after a brake hydraulic pressure control unit has been mounted in the engine room of a vehicle, external pipes are connected thereto from above the unit. In order to smoothly connect pipes to the unit, ports to be connected to the master cylinder, wheel cylinders and reservoir are formed in the hydraulic block at its upper portion. Thus, if the component parts forming each of a plurality of hydraulic circuits are arranged in the lateral direction, the brake fluid passages (oil lines) for each hydraulic circuit have to be markedly displaced in the lateral width direction in order to connect them to the respective ports while avoiding interference with component parts and brake fluid passages for the other hydraulic circuits. This naturally results in increased lateral width of the hydraulic block. In an arrangement in which component parts forming a first hydraulic circuit are provided on the substantially upper half portion of the hydraulic block and component parts forming a second hydraulic circuit are provided on the substantially lower half portion of the hydraulic block, with the component parts of each hydraulic circuit arranged in the lateral direction, it is necessary to connect the component parts provided on the lower half portion to the ports at the upper portion of the hydraulic block, while avoiding interference with the component parts provided on the upper half portion of the hydraulic block. This arrangement, therefore markedly increases the lateral width of the hydraulic block and thus the entire unit.